Transcript Slide - Fort Lewis College

Charles Hakes
Fort Lewis College
1
Charles Hakes
Fort Lewis College
2
Chapter 12
Stellar Evolution/
Supernovae
Charles Hakes
Fort Lewis College
3
Outline
• Test 3 Wednesday
• Death of Low-mass Stars
• Death of High-mass Stars
Charles Hakes
Fort Lewis College
4
Current Events
• http://apod.nasa.gov/apod/ap111109.html
• http://www.youtube.com/watch?feature=pla
yer_embedded&v=vtEvuz_oQ5o
• http://www.space.com/scienceastronomy/g
reen-brown-dwarf-star-spotted101110.html
• http://news.discovery.com/space/top-5space-spirals.html
Charles Hakes
Fort Lewis College
5
Figure 12.10
White Dwarf
on H–R Diagram
12 - For 1 solar mass
stars, that is all that
will fuse.
•
(need 600 million K
for the next reactions
to occur.)
•
The outer shell gets
“blown off” by the
hot, dense, core.
•
Result is a planetary
nebula around a
white dwarf (13).
Charles Hakes
Fort Lewis College
6
Figure 12.9
Planetary Nebulae
Charles Hakes
Fort Lewis College
7
Figure 12.12
Distant White Dwarfs - globular cluster M4
Charles Hakes
Fort Lewis College
8
Figure 12.11
Sirius Binary System - nearby example of a white dwarf
Charles Hakes
Fort Lewis College
9
Figure 12.14
Close Binary System
Charles Hakes
Fort Lewis College
10
Figure 12.13ab
Nova
•
•
Charles Hakes
Fort Lewis College
11
A nova forms when
the temperature in
the accretion disk
reaches 107 K (H
fusion).
Such a star might
“go nova” dozens (if
not hundreds) of
times.
Figure 12.13c
Nova
Charles Hakes
Fort Lewis College
12
Figure 12.15
Nova Matter Ejection
Charles Hakes
Fort Lewis College
13
High Mass Stars
Charles Hakes
Fort Lewis College
14
Figure 12.16
High-Mass
Evolutionary Tracks
•
•
Charles Hakes
Fort Lewis College
15
Intermediate mass
(~4 Msun) stars fuse
carbon, but end up
as white dwarfs.
High mass (>10 Msun)
stars evolve rapidly.
Helium (and other)
fusion begins before
the star ever gets to
the Red Supergiant
stage.
Figure 12.16
High-Mass
Evolutionary Tracks
Charles Hakes
Fort Lewis College
16
•
Wolf Rayet stars (are
really big ones) have
very strong winds.
•
http://upload.wikimedia.org/wi
kipedia/commons/4/49/Crescen
thunter.jpg
When fusion is happening in the core of a
star, the core is
A) heating and shrinking
B) heating and expanding
C) cooling and expanding
D) in equilibrium
Charles Hakes
Fort Lewis College
17
When fusion is happening in the core of a
star, the core is
A) heating and shrinking
B) heating and expanding
C) cooling and expanding
D) in equilibrium
Charles Hakes
Fort Lewis College
18
When fusion stops in the core of a star,
the core is
A) heating and shrinking
B) heating and expanding
C) cooling and expanding
D) in equilibrium
Charles Hakes
Fort Lewis College
19
When fusion stops in the core of a star,
the core is
A) heating and shrinking
B) heating and expanding
C) cooling and expanding
D) in equilibrium
Charles Hakes
Fort Lewis College
20
Figure 12.17
Heavy Element Fusion
•
Each stage is faster
than the stage
before.
•
•
•
•
•
Charles Hakes
Fort Lewis College
21
H - 10 million years
He - 1 million years
C - 1000 years
O - 1 year
Si - 1 week
Figure 12.17
Heavy Element Fusion
•
Charles Hakes
Fort Lewis College
22
Fusion of iron does
not produce energy!
Core-Collapse
• The iron core shrinks and heats.
• Photons are energetic enough to photodissociate iron nuclei.
• Iron converted back to protons and
neutrons.
• This uses up energy - reduces pressure
• Collapse accelerates!
Charles Hakes
Fort Lewis College
23
Core-Collapse
• Protons and electrons combine to form
neutrons releasing neutrinos.
• Collapse continues until neutrons are in
contact with each other.
• Core “rebounds” and a shock wave throws
off the outer layers of the star (mostly H
and He.)
Charles Hakes
Fort Lewis College
24
Core-Collapse
• Protons and electrons combine to form
neutrons releasing neutrinos.
• Collapse continues until neutrons are in
contact with each other.
• Core “rebounds” and a shock wave throws
off the outer layers of the star (mostly H
and He.)
• This collapse takes about 1 second!
Charles Hakes
Fort Lewis College
25
Figure 12.18
Supernova 1987A
Charles Hakes
Fort Lewis College
26
Recent Supernovae
Charles Hakes
Fort Lewis College
27
Recent Supernovae
Charles Hakes
Fort Lewis College
28
Figure 12.19
Supernova Light Curves
Charles Hakes
Fort Lewis College
29
Figure 12.20
Two Types of Supernova
Charles Hakes
Fort Lewis College
30
Carbon Detonation (Type I) Supernova
• Recall the accretion around a white dwarf
star.
• When the star reaches 1.4 Msun, the
density and temperature allow carbon to
finally fuse.
• It fuses everywhere simultaneously.
• Almost no hydrogen observed in the
spectrum of Type I supernova.
Charles Hakes
Fort Lewis College
31
Figure 12.21
Supernova Remnants
Charles Hakes
Fort Lewis College
32
Formation of Heavy Elements
• Elements heavier than iron require energy
input for creation.
• Supernovae provide the energy source.
• The expanding cloud contains primarily H
and He, but is enriched in heavy elements.
• The Sun was created from “enriched”
interstellar gas and dust.
Charles Hakes
Fort Lewis College
33
More Precisely 12-1
The Cycle of Stellar Evolution
Charles Hakes
Fort Lewis College
34
Three Minute Paper
• Write 1-3 sentences.
• What was the most important thing
you learned today?
• What questions do you still have
about today’s topics?
Charles Hakes
Fort Lewis College
35